Research on Parallel Reactive Power Sharing and Port Voltage Compensation Strategy of Microgrid Inverters

The parallel system of microgrid inverters mostly adopts droopy control method, which can distribute the output power of inverters according to the state of microgrid. However, when the line impedance is different, the traditional sag control can not make the output reactive power evenly distributed according to the sag coefficient, and reactive power circulation exists in the system. A control strategy based on variable sag coefficient of inverter output reactive power difference combined with port voltage compensation is proposed. Through the voltage and current double closed-loop parameter design, the active power and reactive power are decoupled, and the output impedance is approximately sensitive to the line impedance, which makes the parallel system suitable for P-ω/Q-V sag control equation. The average value of the output reactive power of two inverters is introduced to realize the variability of sag coefficient in the reactive power-voltage link. The reference voltage is introduced proportionally and the output voltage deviation is suppressed by integral compensation. Simulation and experimental results show that the proposed strategy can equalize reactive power in different line impedance systems and effectively suppress reactive power circulation.